Now, with his case headed to the Ontario Court of Appeal, he stands as a shining example of perhaps the most frustrating dilemma in jurisprudence -- that while it is frequently difficult to prove a suspect's guilt, it is nearly impossible for the wrongly convicted to prove their innocence.

What is less obvious -- even after the high-profile public inquiries into such grievous legal errors as the prosecutions of Guy Paul Morin and Thomas Sophonow -- is why these wrongful convictions happen.

In the words of James Lockyer, a celebrated defence lawyer who has represented many wrongfully convicted people in Canada, including Truscott: "The causes are as infinite as there are cases."

This may be true, but there are some notable and revealing trends.

A survey of 205 wrongful convictions in the United States prior to 1988, for instance, concluded that eyewitness misidentification was responsible for just over half of them, followed in roughly equal proportions by witness perjury, negligence on the part of criminal justice officials, "pure error" and coerced confessions.

Explicit framing or perjury by investigators made the list, but only just, and questionable or mistaken forensic science -- which has emerged in the last 20 years as a key factor in nearly all Canadian cases of wrongful convictions -- barely registered at about 1%.

If this survey were to be conducted again, the results would likely change -- a greater proportion would be due to forensic science errors, perhaps, especially in cases of hair microscopy, and there might also be an increase in prosecutorial negligence, given the stricter standards that have been imposed on Canadian Crown attorneys -- but not necessarily for the better.

A look at some of Canada's most notable cases reveals a judicial system stubbornly slow to learn from its frequent mistakes.

FELIX MICHAUD AND SECRET EVIDENCE

Although it is rarely a central factor, a weak or inexperienced defence lawyer turns up with alarming regularity in cases of wrongful conviction. Frequently, their central error is in failing to acquire or fully appreciate all the evidence that police have compiled against the accused.

This is not always the defence lawyer's fault.

Before 1991, Crown prosecutors in Canada were obliged to disclose only the evidence they judged to be reliable, relevant and legally admissible. Now, however, after a Supreme Court of Canada ruling in a case involving a lawyer fighting breach of trust, theft and fraud charges, they must disclose nearly everything, but old habits die hard. For evidence, one need look no further than the 1993 murder prosecution of Felix Michaud of New Brunswick, whose conviction was overturned in 2001 due to ''the high degree of negligence demonstrated by the Crown in failing to disclose evidence [a wiretap tape recording that appeared to exonerate Mr. Michaud] that was beneficial to the defence.''

ROBERT BALTOVICH AND EYEWITNESS TESTIMONY

The Ontario Court of Appeal, which will hear Truscott's case, is now deliberating over the decade-old conviction of Robert Baltovich, whom a jury convicted of killing his girlfriend, Elizabeth Bain. Evidence has since emerged, however, that points to Baltovich's innocence and the possible guilt of serial killer Paul Bernardo.

The Crown's case was entirely circumstantial, and relied heavily on the "hypnotically refreshed" testimony of eyewitnesses who placed Baltovich at various places that fit with the Crown's theory about Ms. Bain's murder. One major complaint in the appeal was that an eyewitness who picked Baltovich out of a lineup had been shown the photos all together, rather than one at a time.

This may seem a minor point, but psychological research has shown that witnesses -- under pressure to be helpful -- will frequently point to the person who most resembles their memory of the suspect.

The inquiry into the wrongful conviction of Thomas Sophonow made the recommendation that police use only sequential lineups (one picture at a time, until the witness makes an identification) not simultaneous lineups. This is a recommendation, though, not a law, and police do not always follow it.

"There are no rules about what police can and cannot do [with lineups], and we are going to continue to have eyewitness identification problems in Canada until there are," Mr. Lockyer said.

The central problem with eyewitnesses is that their confidence rarely matches up with their reliability. This is vexing for the courts, as confident witnesses make convincing witnesses.

The American psychologist Elizabeth Loftus, the grandmother of the field of eyewitness fallibility, has shown in dozens of ways that, with a little suggestion, witnesses can be certain they saw something, when in fact they never did. Although the issue is dead serious in murder convictions, her experiments are often hilarious, such as when people swear on their life that they met Bugs Bunny at Disney World. Bugs, of course, is a Warner Bros. character, who would never turn up at the theme park.

GUY PAUL MORIN AND FORENSIC SCIENCE

For all the advances in law and police procedure, nothing has changed so much in the last 20 years as forensic science. DNA analysis, especially, has grown from science fiction into a powerful tool for both prosecution and defence.

Hair analysis under a microscope, on the other hand, which played a crucial role in the conviction of Mr. Morin , among several others, has been largely undermined.

The Association in Defence of the Wrongly Convicted, of which Mr. Lockyer is a director, has been pressing provincial governments to re-examine every case that relied on hair microscopy in the last 20 years.

So far, only Manitoba -- home to wrongfully convicted James Driskell and Thomas Sophonow -- has complied. And just last month, the Manitoba Attorney-General's office announced that two more cases (out of 39 to use hair analysis) had failed a follow-up DNA analysis.

DAVID MILGAARD AND PUBLIC BLOODLUST

Mr. Lockyer scoffs at the common perception that wrongful convictions tend to befall funny ducks -- people who, by virtue of their own peculiarity or eccentricity, inevitably draw police suspicion upon themselves.

They are not "weird, peculiar, strange or whatever," he said. "I think rather the contrary, that they're perfectly normal but they get demonized by investigators."

Thus did Guy Paul Morin become the creepy guy who lived next door to the murdered girl and fit the FBI profile of the killer (it later emerged at a public inquiry that this profile had been tailored to fit him). David Milgaard, too, was cast a suspicious hippie in the Gail Miller murder investigation.

And perhaps -- the Ontario Court of Appeal has not yet ruled -- straight-laced university student Baltovich was wrongly cast a fiendish criminal mastermind, able to send up a smokescreen of circumstantial evidence to confuse the police.

Of course, as Mr. Justice Michael Moldaver, one of three judges on the Baltovich appeal, observed in an off-the-cuff courtroom comment: "So many things can be seen as deception if you presume he's guilty."

ROMEO PHILLION AND FALSE CONFESSIONS

In custody on a robbery charge in the early 1970s, Romeo Phillion falsely confessed to murdering Ottawa firefighter Leopold Roy. He recanted, but not before the wheels had been set in motion that would see him wrongly convicted.

Mr. Lockyer believes people make false confessions for two main reasons. One, which he said applies in the Phillion case, is a desire for notoriety, to seek out those 15 minutes of fame, or at least infamy.

"That 15 minutes turned into 32 years," Mr. Lockyer said.

In the case of Kyle Unger, a Manitoba case that also involved faulty hair microscopy, police elicited a confession by posing as drug dealers and Unger, who maintains his innocence, said he falsely confessed to murder because he was hoping to impress them.

The other reason is police pressure, which Mr. Lockyer said has been especially troublesome when the subject is developmentally delayed.

In his book Police Interrogation, Canadian criminologist R.S.M. Woods outlines the various forms this pressure can take. In addition to the good cop-bad cop strategy, he describes the techniques of intimidating exaggerations (theft is armed robbery, assault is attempted murder); of police pretending to have more evidence than they actually do (which can often backfire); of ego-deflation ("You're too stupid to have robbed that bank."); ego-inflation ("Wow, what a brilliant crime. Tell me about it."); blaming the victim, which works especially with sexual crimes; the "you did nothing wrong" approach, in which police might ask about the "accident," and the "speak now or regret it later" approach.

LONG-TERM CONSEQUENCES

For his analysis of the psychological effects of wrongful convictions, British psychologist Dr. Adrian Grounds set out expecting to find nothing special. Most wrongfully convicted people enter prison with relatively stable emotional lives, and the consensus in the scientific literature is that long-term incarceration does not cause significant psychological deterioration.

But in wrongful convictions, he found the situation is far different; these men had become wrapped in chronic fear, and were unable to pursue the intimacy with their families that might have saved them.

''Those who had been in prison for longest had lost a generation of family life. Parents had died and children had grown up. Young men who entered prison as fathers of young children were released as middle aged men with grandchildren,'' he wrote.

Aside from the understandable feelings of bitterness and loss, Dr. Grounds found, the 17 men he studied ''had marked features of estrangement, loss of capacity for intimacy, moodiness, inability to settle and loss of a sense of purpose and direction.''

In all but three of those cases, he found their twisted emotions had caused such significant impairment that it fit the World Health Organization's definition of ''enduring personality change after catastrophic experience.''

In his report on the Sophonow case, Mr. Justice Peter Cory argued that, psychology aside, the very fact of wrongful conviction creates an entitlement to financial compensation. This is not yet enshrined in law, though, and so the wrongfully convicted often try to prove that police were doing more than just investigating them aggressively; that they were dishonest and malicious.

Once the rest of society has moved on from a tragedy, however, it can be difficult to rally support for such a cause, which, like many lawsuits, can smack of opportunism.

And so these people, overwhelmingly men, are often left alone with the sad fact, as expressed in the Tragically Hip song about David Milgaard, that "no one's interested in something you didn't do."